The only thing other than 91 is the race gas at the stations near Wildhorse Pass (Firebird race track) and Tom's Thumb in scottsdale.
You can also buy 5 gallon jugs of Sunoco race gas from a couple places in town - or they sometimes have them for sale at shows like GoodGuys, and the larger drag events at Wildhorse. Then mix it in with 91 as needed.